AstraZeneca has filed a lawsuit in the US District Court for the Eastern District of Missouri against the generic company KV Pharmaceuticals, for patent infringement.

The lawsuit is the result of a Paragraph IV Certification letter submitted by KV Pharmaceuticals to AstraZeneca concerning its intent to manufacture and sell metoprolol succinate in the 200 mg dose form in the United States.

Metoprolol succinate is marketed as Toprol-XL in the U.S. by AstraZeneca, LP. In 2002, Toprol- XL had US sales of $617m. Of these sales, 12% were in the 200mg dosage.

The basis for AstraZeneca's complaint is that the action taken by KV infringes AstraZeneca's patents covering Toprol-XL.